Evaluation of Marginal Leakage and Strength of Dental Resin Cement Based on Fracture Mechanics

点击翻译按钮获取中文摘要

We study here the mechanical properties such as adhesive strength and marginal leakages of dental resin cements with the use of fracture mechanical approaches, and obtained the following results :1. The degenerations are induced both in the resins themselves and along the adhesive interfaces. So we first examined the effects of mechanical and environmental factors to the resins by the experiments utilizing the resin specimens and the holders which enable us to apply tensile forces to the specimens in hot water bath. The specimens immersed in hot water without tensile force and those in air with tensile force do not show decrease of adhesive strength. On the other hand, specimens in hot water with tensile force show the considerable decrease of adhesive strength with time.2. On the fracture surface of the above specimens, we could not identify any significant patterns. Hence the degenerations from mechanical and environmental factors are considered to be induced in resin matrix itself.3. Then we examined the strength of adhesive interfaces by the use of DCB specimens with constant opening force and WOL specimens with constant displacement. The specimens are made of stainless steel and the resin cements are either Panavia or Superbond, both of them are popular dental materials in japan. For DCB specimens are instrumented with displacement gauges and load cells for WOL specimens.4. We observed crack openings for Superbond specimens which increase with time, indicating the crack propagations or elongations of resin matrix proceeding the final failure. On the other hand, the crack opening are hardly detectable and the starting of crack propagation immediately succeeded by final failure.5. On the fracture surface of specimens, both of adhesive and cohesive fractures are observed. We conclude that the degenerations are induced in the resin matrix and along the interface, and the mechanical properties of resin cement determined the failure mode.